The romantic novelist:

What love is depends on where you are in relation to it. Secure in it, it can feel as mundane and necessary as air – you exist within it, almost unnoticing. Deprived of it, it can feel like an obsession; all-consuming, a physical pain. Love is the driver for all great stories: not just romantic love, but the love of parent for child, for family, for country. It is the point before consummation of it that fascinates: what separates you from love, the obstacles that stand in its way. It is usually at those points that love is everything

The insufferably cute kids:

I guess my best way of explaining what I think love is would be like the solar system. There are a bunch of planets that can represent people. And then of course gravity holds them together. And gravity is sort of like love. No matter how far apart people are, love can hold them together

The psychotherapist:

Aaron Balick is a clinician and cultural theorist who applies contemporary psychoanalysis as a means of understanding modern life, as exemplified by his book The Psychodynamics of Social Networking.

Sameness is easy. It’s difference that’s the real challenge. Romance is captivating, but the monotony of busy lives can be deadening. Harmony is mesmerising, but discord and conflict can feel destructive. Many think that love is about always being on the same page with our partner, feeling romantic and living in harmony. Threats to these experiences can feel like obstacles that get in the way of love. But love is as much about the obstacles as it is about the bliss. Love is accepting difference, recovering from conflict and tolerating discord. Fundamentally, love is allowing your partner to be entirely who they are, even when their very being needles you to the core. It is a profound acceptance of the personhood of your lover, while dropping your need for them to be anything different. Yes, it’s a tall order. But who said it was going to be easy?

America’s longest married couple:

Ann and John Betar eloped and got married in 1932. Ann says the secret to their successful marriage is that it isn’t “lovey dovey” all the time, and that their main interest is raising the children.

John says that the only thing they ever row about is the cooking. Ann replies: “See ... that’s what he thinks.”

For Valentines’ Day this year, they will be taking part in a Twitter Q&A about what keeps a relationship going as long as theirs, using #LongestLove. Although they may not know what they have let themselves in for with that hashtag.

The singer-songwriter:

Howard Jones hit #2 in the UK chart with his second single What Is Love? in 1983.

Love is letting each other be who we are without fear of censure. Love is not wanting the other to become a clone of ourselves. ‘Other’ offers resistance, pushing us to find what is self. Love is actively embracing our equality and pushing each other to realise our full potential and make our full contribution to the world. Love is facing forward, both fighting for a common goal – both strong, both independent and positively choosing a knowing dependence. Love is always leaving the door unlocked and continuing that love when ‘other’ may choose to use the exit. Love is letting go and wishing well. Love is aching joy. Love is the safe haven. Love is arriving home

The physicist:

Jim Al-Khalili is a theoretical physicist and science writer. Speaking in 2012, he said:

Jim-Al-Khalili

Biologically, love is a powerful neurological condition like hunger or thirst, only more permanent. We talk about love being blind or unconditional, in the sense that we have no control over it. But then, that is not so surprising, since love is basically chemistry. While lust is a temporary passionate sexual desire involving the increased release of chemicals such as testosterone and oestrogen, in true love, or attachment and bonding, the brain can release a whole set of chemicals: pheromones, dopamine, norepinephrine, serotonin, oxytocin and vasopressin. However, from an evolutionary perspective, love can be viewed as a survival tool – a mechanism we have evolved to promote long-term relationships, mutual defence and parental support of children, and to promote feelings of safety and security

The poet:

Love is more than what can be expressed in words, love is more than grammar and verbs. Love is compassionate and soothing, love can be painful and gruelling; but only for growth. Love is not abusive, love is not vindictive, love is not selfish. Love will not leave you with a black eye and hating yourself. Love is the building blocks of creation, love is the substance from which we are made. From love, to love, by love

The nun:

Love is more easily experienced than defined. As a theological virtue, by which we love God above all things and our neighbours as ourselves for his sake, it seems remote until we encounter it enfleshed, so to say, in the life of another – in acts of kindness, generosity and self-sacrifice. Love’s the one thing that can never hurt anyone, although it may cost dearly. The paradox of love is that it is supremely free, yet attaches us with bonds stronger than death. It cannot be bought or sold; there is nothing it cannot face; love is life’s greatest blessing